The present invention relates to power take-off gearing for agricultural and industrial applications, and more particularly to a three-speed power take-off assembly having one shift fork.
Power take-off (PTO) assemblies typically are coupled to a power source, such as an internal combustion engine. In some applications, the PTO assembly is attached to a transmission gear box and in other applications it is attached directly to a clutch and the output shaft of the power source.
In the agricultural industry, a PTO assembly is mounted on a tractor and is used to provide rotational motion to one or more farm implements being operated in conjunction with the tractor. The power source of the tractor provides the input power to the PTO assembly. Generally, the PTO assembly houses gear trains that will produce several speeds of rotation of the PTO output shaft. Typical PTO assemblies provide two speeds of rotation, i.e., 540 RPM and 1000 RPM and use one shift fork to move between the two gear trains to produce such speeds of rotation. As more farm implements and different applications of farm implements became available, additional speeds of rotation of the PTO output shaft was desirable or required. However, one shift fork can alternatively engage only two gear trains so in order to provide more than two output speeds of rotation, additional gear trains and shift forks are required to provide three or more speeds of rotation. In other words, in order to obtain three speeds of rotation for the PTO assembly, four gear trains and two shift forks were required. Such arrangements increased the cost of the PTO assembly, as well as increased the complexity of the operation and size of the PTO assembly. The operator of the PTO assembly had to properly select the position of the several shift forks to obtain the appropriate or proper speed of rotation of the PTO output shaft. Some previous PTO assemblies eliminated one gear train but still required two shift forks to obtain a three speed PTO assembly.
Thus, there is a need for a three speed PTO assembly that will provide three speeds of rotation of the PTO output shaft with three gear trains and only one shift fork. There is also a need for a three speed PTO assembly that is simple, and compact to obtain the optimum efficiency between the speed of the power source and an implement""s operating RPM.
According to the present invention a power take-off assembly having three output speeds suitable for a work vehicle or a power station is provided. The PTO assembly supplies rotational motion to at least one piece of equipment used in conjunction with a power source. The power source can be mounted on a work vehicle or in a power station. The PTO assembly is coupled to the output shaft of the power source and comprises a PTO housing with an input shaft and an output shaft rotatably mounted in the housing in a spaced apart parallel relationship. Each shaft has mounted on it three gears with corresponding gears on each shaft intermeshed. The input shaft has the three fixed drive gears. The output shaft has a high gear ratio gear and intermediate gear ratio gear each mounted to freewheel until engaged to the output shaft by a splined shift hub moved by a single shift fork. The output shaft also has a low gear ratio gear mounted on an overrunning clutch which allows the low driven gear to freewheel when either of the high driven gear or the intermediate driven gear is engaged to the output shaft.
Further characteristics and advantages of the present invention will become apparent during the course of the following description, given by way of example only and without any restrictive nature.